Radio system for collision prevention



Feb. 14, 1939. F. w. DUNMORE 2,146,724 RADIO SYSTEM FOR COLLISIONPREVENTION Filed y 1933 2 Sheets-Sheet .1

II II Feb. 14, 1939.

F. w. DUNMORE 2,146,724 RADIO SYSTEM FOR COLLISJ ION PREVENTION FiledMay 11, l933 2 Sheets-Sheet 2 FIGURE 2 A? I m Kym, qJ

gin/09mm JW 209W the and a directional secondary Patented Feb. 14, 1939UNITED STATES RADIO SYSTEM Fon COLLISION PREVENTION Francis W. Dunmore,Washington, D. 0., assignor to the Government of the United States,

rep-

resented by the Secretary of Commerce Application May 11,1933, SerialNo. 670,423

2 Claims.

(Granted under the act of March 3, 1883, as

' amended April 30, 1928; 370 0.

The invention described herein maybe manufactured and used by or for theGovernment of United States for governmental purposes only, without thepayment of any royalty thereon.

mitter and receiver for use on a mobile. object, both receiver andtransmitter operating on the same radio frequency and both operating ineffect simultaneously, thatis, at an audio frequency rate or higher,without interference. The receiver having a directive antenna makespossible the determination of the direction to a second mobile objectequipped with similar apparatus, thus avoiding a possible collision.

In this invention the transmitting set and receiving set are operated ina push-pull fashion such that when the transmitter is in operation thereceiver is rendered inoperative. This changeover is made suflicientlyrapid that the receiver is in effect continuously operative for thedetection of signals from a second mobile object. Other uses for andadvantages of my invention will be more clearly understood by referenceto the following description and diagrammatic drawings.

In these drawings- Figure 1 shows the circuit arrangement of one form ofmy invention in which a high frequency transmitting and receiving setare used with a double transmitting antenna to prevent shadows receivingantenna.

Figure 2 shows the application of this invention to an airplane when.the two transmitting antennas are located on the wing tips and thedirectional receiving antenna amidship.

Figure 3 shows the application of my invention to the marine type of lowpower mobile beacon now coming into use, showing the ships directionfinder which may function while the mobile beacon is operating on thesame radio frequency and on the same ship without interference.

In the form illustrated in Figure 1 the output from a high frequencytransmitting set, I serves as a means for feeding antennas 2 and 3through transmission lines 4 and 5. The'antennas 2 and 3 are so locatedone on each wing tip that a signal will be sent'in all horizontaldirections without shadow effects. with one end of the secondarysupplying power to the plates of transmitting set I. A resistance 1shunted across part of this same end of the supplies negative biasvoltage to the grid of last tube 8 in a high frequency receiving set 9.The other portion of this secondary sup- My invention relates to acombination trans- 6 is a center tap transformer plies the plate oftransformer. A circuit the tube 8 through an audio I2 may be of thesuperregenerative type, the input of which is connected to a directionantenna I3 which may be orientable about a vertical axis and collapsibleso that it folds down within the airplane. I4 is an oxide rectifier andI a current indicating means. A- direct current bias is supplied from asuitable source, which may be a battery I6. The alternating current biason the grid of the tube 8 may be set at the proper value reading on I5with no signal coming in; by means of a slider I1. Alternating currentis supplied from a suitable source I8.

The circuit functions as follows: This transmitter functions alternatingcurrent voltage supplied at I 8, when the plates of the tubes in thetransmitting set I become positive. During this half-cycle, however, theplate of the tube 8 is negative rendering it inoperative so that thesignal sent out by I cannot be received on indicator I5. However, duringthe next half of the cycle of the current supplied at I8, the plates ofthe tubes in the transmitter I become negative, rendering this unitinoperative while the plate of the tube 8 becomes positive allowing thistube to pass on any signal coming in on the grid of this tube. When theplate of the tube 8 is positive, the grid is made sufiiciently negativeby means of the battery I6 and the position of slider I! on theresistor 1. Thus, during every alternate half-cycle of the voltagesupplied at I8, the transmitter I operates and the receiver 9 is deadand during the intermediate alternate half-cycle the transmitter I isdead and the receiver 9 is functioning. By means of the directiveantenna I3 which is rotatable about a vertical axis, the direction 01'the signal being received by 9 may be determined by manually rotating itto determine the position for a maximum signal.

With this arrangement, therefore, a mobile object may send a continuoussignal of a note depending upon the frequency of the current supplied atI8, which signal will be detected by a second mobile object in theneighborhood, while at the same time the directional receiver on thefirst mobile object functions continuously to detect the signal sentfrom the second mobile object. As there are no synchronizing meansbetween the transmitters on the various mobile obiects and difierentfrequencies may be used at I8, the receiver 9 will always beintermittently operating during some portion of the cycle oftransmission of other transmitters.

during that half-cycle of the igure 2 illustrates another form of myinvenas applied to an aircraft. Here l8 repreas the aircraft; 2 and 3the vertical doublet ennas for transmitting the warning signal inhorizontal directions. l3 represents the ditional receiving antennarotatable about a tical axis and collapsible into the wing as wn at 20.4 and 5 represent the transmis- 1 lines, I the transmitting set, and 9the reving set. igure 3 shows an application of my invention era a lowerradio frequency is used such as marine use. Here 2| represents anon-direcnal transmitting antenna, 22 is a standard 7 power marinebeacon transmitter such as are nmonly used, 6 is a center taptransformer one le of the secondary of which supplies. plate itage tothe tube 23 of the transmitter 22 and e other side In supplying platevoltage to the st tube or two tubes in a direction finder reiving set24. 25 is a direction finder coil rotable about a vertical axis. Thesecircuits nction as explained under Figure 1, except at lower radiofrequency. While the above are forms of my invention, is understood thatother means of applying the )ltage from transformer 6 to the receivingset my be used to render it operative and then ioperative. Therefore, Ido not wish to be limed to these specific embodiments, sincemodificaions may be made both in the circuits and aparatus within thescope oi! my invention.

Among such modifications would be the inclusion of an audible signaldevice in the output of tube 8.

What I claim is:

1. In a radiant energy system for indicating the close proximity of onecraft to another craft, means carried by each of said craft fortransmitting vertically polarized radiant energy of a preselected wavelength from each of said craft in all azimuthal ried by each of saidcraft for directionally receiving the vertically polarized radiantenergy of preselected wavelength transmitted from other craft, switchingmeans carried by each of said craft for alternately putting intooperation the transmitting means and the receiving means carried by saidcraft, and means for operating the switching means carried by ferentfrequencies, whereby the receiving means carried by each of said craftwill be cyclically put into operation during a part oi! the time thetransmitting means carried by any and all other craft is energized.

2. A system as set forth in claim 1 in which the wave length of theenergy transmitted is small iii-comparison to at least one physicaldimension of the craft carrying the means for transmitting verticallypolarized radiant energy.

FRANCIS W. DUNMORE.

directions in space, means car- 1 each of said craft at dif-

